The present invention relates to an improvement in shaft, grip and socket which are used for a golf club.
The shaft of a conventional golf club is designed in a pipe structure having a circular section. Further, the grip of the golf club is normally formed of rubber or the like and designed in a cylindrical shape, and the base end of the shaft of the golf club is inserted and fitted into the cylindrical grip. The socket of the golf club is designed in a cylindrical shape so that the shaft is inserted in the cylindrical socket. The tip portion of the shaft is inserted into the hosel portion of the head and adhesively fitted therein while the shaft is inserted in the socket.
Such a conventional shaft is designed to be uniform in weight in the circumferential direction, and this design provides high balance to the operability of the shaft when the shaft is used alone. However, when the shaft is fitted to the head, the weight balance of the overall club to the shaft center axis is bad. That is, most of the head weight acts outwardly from the shaft center axis, and thus the centrifugal force which is applied during a swing motion magnifies the outward turning motion, so that the operability of the club and the reproducibility of the swing motion are lowered.
That is, the golf swing is greatly dependent on the gripping way of the grip. Even in the case of a club which is functionally excellent, the excellent function of the club cannot be effectively used if the grip thereof is bad.
In the case of the human, the thumb and the index finger are most frequently used in daily life an d they can easily strengthen the force thereof. However, unlike a swing robot, the outward turning motion causes the underarm to be easily opened. Therefore, there has been required such a technique that the underarm is forcedly closed by the force at the little finger side, that is, at the inside of the grip, and the operability of the club and the reproducibility of the swing are enhanced by positively utilizing the motion that the club is separated from the human body due to the centrifugal force during the swing motion.
However, general golfers use the force at the thumb side more excessively as the weight of the shaft is reduced. In this case, the speed of the swing motion increases, but the motion is liable to be shifted to the outward turning motion. Consequently, as the shaft and the grip are reduced in weight, the head speed increases, but the outward turning motion is magnified because the weight at the hand side is excessively light. Accordingly, for the general golfers, the head speed is increased because the performance of the club is enhanced, but the operability of the club and the reproducibility of the swing motion are little improved. That is, the golf technique of the general golfers are little improved in spite of the improvement in performance of the club, and they cannot effectively use the improved performance of the club.
Further, even when the shaft and the grip are further reduced in weight, there is no difference in weight between the outside and the inside with respect to the shaft center axis. Accordingly, the general golfer who originally has an unstable swing arc cannot change their unstable swing motion even when the shaft and the grip are designed to be further light in weight.